If you find you have a clicky jaw, have difficulty opening wide, or suffer from jaw pain or recurrent headaches you may in fact be suffering from a condition called TMJDS:

TMJDS (temporomandibular joint dysfunction syndrome) is an umbrella term covering clinical manifestations due to disfunction of the jaw joint and associated muscles.  TMJDS is a very common condition.  Signs and symptoms may include jaw joint sounds, a limitation in mouth opening, pain in or around the ears (the jaw joint), locking of the jaw and pain when chewing.

Treatment of the condition may involve stress reduction techniques, eliminating habits such as nail biting or chewing gum, performing specific exercises or wearing a splint. A splint is a device which fits on to the teeth and is usually worn during sleep. It modifies the way you grind or clench your teeth, reducing the symptoms you experience.  Splints may also be worn to reduce wear on teeth, even if symptoms are not experienced.

There are various types of splint which can be fabricated. They aim to reduce damage caused to teeth by grinding, to align the lower jaw in a more favourable position and to balance the contacts between the upper and lower teeth. They all aim to reduce symptoms associated with TMJDS.